ATI CrossFire and NVIDIA SLI in Terms of CPU Performance

We proceed with the
series of articles, which can be entitled "Nitty-Gritty of iXBT.com
Testlab", devoted to results of our inhouse tests - they can
be interesting to some of our readers. This article will be devoted
to consequences of one our experiment: what if equip CPU testbeds
with the most powerful graphic solution - two video cards in CrossFire
(ATI) or SLI (NVIDIA) mode? There were some disappointments, but the
results were funny. OK, let's see...

Hardware and Software

Testbed configurations

CPU

Motherboard

Memory

Core 2 Duo X6800

ECS nFORCE 570 SLIT-A

Corsair CM2X1024-6400 (5-5-5-12)

Core 2 Duo X6800

Intel D975XBX (BIOS 1334)

Corsair CM2X1024-6400 (5-5-5-12)

A small note: as the CrossFire technology is officially supported
only by motherboards with ATI and Intel 975X chipsets, and SLI is
supported only by motherboards with NVIDIA chipsets, we couldn't assemble
identical testbeds for ATI and NVIDIA video cards. But as it's impossible
(using unofficial hacks in testbeds is not acceptable), our comparisons
of results are quite well posed.

Maya 6.5

Pro/ENGINEER Wildfire 2.0

The situation in a professional engineering package is even worse:
CF and SLI reduce (!) performance in wireframe mode. In Graphics Shade
test, performance slumps only on the testbed with CF. But NVIDIA SLI
brings a meager performance gain.

SolidWorks 2005

The smaller results, the better. Complete fiasco: CF and SLI result
in a performance drop. To be precise: NVIDIA SLI drops performance
only insignificantly, unlike the ATI technology.

F.E.A.R.

Everything falls into place in the first game: SLI and CF work as
they should. Performance gains do not reach twofold, but they are
still significant.

Half-Life 2

One of the most CPU-intensive games is still limited by a processor
even in high quality mode at 1024x768, video cards have nothing to
do with it. At least they don't make it worse, like in professional
packages ;).

Quake 4

Quake 4 benefits from SLI as well as CF.

Unreal Tournament 2004

Old UT2004 also reacts well, but not as much as we'd like. The situation
would have certainly become better at higher resolutions or with AA.
But it's hardly relevant for us, as we analyze CPU performance, not
GPU performance.

Conclusions

Conclusions are crystal clear for those who have scrutinized the
diagrams. It's quite obvious that ATI CrossFire and NVIDIA SLI are
purely gaming technologies so far. They are intended for dynamic 3D
games. Both technologies do not perform well in professional applications.
It would be logical to assume that the problem is not in these technologies,
but in the lack of attention to this tandem from developers. An indirect
proof of this fact is the lack of ATI FireGL for CF. What concerns
NVIDIA Quadro with SLI, we can only point at the drivers: to all appearances,
SLI optimization for professional applications is disabled, if a regular
desktop GeForce is detected (we all hate the so called positioning
so much, don't we? :)).

Thus, considering that the CPU test procedure used in iXBT.com testlab
does not pay major attention to games, it's not expedient to use these
technologies in CPU testbeds. Similar advice can be given to those
users who thought about building CF or SLI tandems for powerful graphics
workstations intended for professional 3D modeling applications and
CAD.